Add a peid2yara script

1 files changed, 113 insertions, 0 deletions

diff --git a/peid_to_yara.py b/peid_to_yara.py
new file mode 100644
index 0000000..975152e
--- /dev/null
+++ b/peid_to_yara.py
@@ -0,0 +1,113 @@
+#!/usr/bin/env python
+# encoding: utf-8
+#
+# Tested on Linux (Ubuntu), Windows XP/7, and Mac OS X
+#
+'''
+untitled.py
+
+Created by Matthew Richard on 2010-03-12.
+Ported to py3 by Julien (jvoisin) Voisin on feb2014
+Copyright (c) 2010. All rights reserved.
+'''
+
+import os
+import re
+import argparse
+import collections
+
+
+def main():
+    parser = argparse.ArgumentParser(description='PEiD to yara rules converter')
+    parser.add_argument('-n', '--no-ep', dest='no_ep', action='store_true',
+        default=False, help='no entrypoint restriction')
+    parser.add_argument('files', metavar='files', type=str, nargs='+',
+        help='scanned filenames')
+    parser.add_argument('-o', '--output-file', action='store', dest='outfile',
+        help='output filename')
+
+    opts = parser.parse_args()
+
+    if opts.outfile is None:
+        parser.error('You must specify an output filename!\n')
+    elif opts.files is None:
+        parser.error('You must supply at least one filename!\n')
+    else:
+        for fin in opts.files:
+            if not os.path.isfile(fin):
+                parser.error('%s does not exist' % fin)
+
+    # yara rule template from which rules will be created
+    yara_rule = '''
+rule %s
+{
+strings:
+    %s
+condition:
+    %s
+}
+
+    '''
+    rules = collections.defaultdict(lambda: set(), {})
+
+    #  read the PEiD signature files
+    data = ' '.join([open(f, 'r').read() for f in opts.files])
+
+    #  every signature takes the form of
+    #  [signature_name]
+    #  signature = hex signature
+    #  ep_only = (true|false)
+    signature = re.compile(r'''
+        \[\d*
+        ([^(?:\->)\n]{1,128})               # This is the rule name
+        (?:\->)?[^\]]*\]\s*\n               # We don't care about content after a "->"
+        signature\ =\ (?:\?.\ )*            # Signature pattern can't start with ??
+        ((?:[0-9A-Fa-f?]{2}\ )*             # Only match hex pairs
+        [0-9A-Fa-f?]{2})\s*\n               # Get the terminal pair
+        ep_only\ =\ (true|false)\s*\n
+        ''', re.MULTILINE | re.VERBOSE)
+
+    # rule name has the same constraints as a C variable name 
+    rules_cpt = 0
+    double_cpt = 0
+    name_filter = re.compile(r'(\W)')
+    for match in signature.finditer(data):
+        name = name_filter.sub('_', match.group(1)).rstrip('_')
+        if (match.group(2), match.group(3)) in rules[name]:
+            double_cpt +=1
+        rules[name].add((match.group(2), match.group(3)))
+        rules_cpt += 1
+    print('[+] Found %d signatures (%d duplicates) in PEiD input file' %
+            (rules_cpt, double_cpt))
+
+    output = ''
+    for rule in list(rules.keys()):
+        detects = ''
+        conds = '\t'
+        counter = 0
+        for (detect, use_ep) in rules[rule]:
+            # create each new rule using a unique numeric value
+            # to allow for multiple criteria and no collisions
+            detects += '\t$a%d = { %s }\n' % (counter, detect)
+
+            if counter > 0:
+                conds += ' or '
+
+            # if the rule specifies it should be at EP we add
+            # the yara specifier 'at entrypoint'
+            conds += '$a%d' % counter
+            if use_ep == 'true' and opts.no_ep is False:
+                conds += ' at entrypoint'
+            counter += 1
+
+        # add the rule to the output
+        output += yara_rule % (rule, detects, conds)
+
+    # could be written to an output file
+    with open(opts.outfile, 'w') as fout:
+        fout.write(output)
+
+    print('[+] Wrote %d rules to %s' % (len(rules), opts.outfile))
+
+if __name__ == '__main__':
+    main()